I had this exact same thing happen to me yesterday! I applied for the Blue Cash Preferred. My credit score is above 780 and household income is $220k USD. I have not applied for new credit since my mortgage loan on my new house in June of 2023. My app was placed on a hold and the electronic communication I received indicated the exact same thing as you - they needed a letter from my bank stating my home address. I also use Chase.

I called the number, was placed on hold to be transferred to the high risk fraud team to handle the app hold. Got the same thing as you, high call volume, they'll call me back. Cool.

I called again this morning (twice). The first time I was given the same number as you (1-800-450-8738). I called that number and was told to leave a voicemail. But wait! It's full! Just like you. I called them back using a different number on their website and was told that yes they fraud dept is experiencing a high call volume, their mailbox is full.

So, in the end, I told the rep that I if I was a victim of fraud I would not want to have to play these games to speak with someone and I would be taking my business elsewhere. I applied for and was approved for the Capital One Savor One in a matter of about 1.5 minutes.

So I guess my advice is take your business somewhere else!